Stent grafts are used to replace or repair vessels of the body such as the arteries. A stent graft is usually formed from a tubular body of a biocompatible graft with one or more stents mounted into or onto the tubular body to provide support therefor. The stents may be balloon expandable stents or self-expanding stents.
Endovascular methods have been proposed for treatment of an aneurysm of the aorta particularly where the aneurysm is adjacent the aorta bifurcation. However, when an aneurysm occurs higher up in the aorta, in the region of the descending aorta adjacent the thoracic arch or in the ascending aorta, endovascular techniques for treating these aneurysms are somewhat more difficult because of the tight curvature of the thoracic arch, the occurrence of major arteries in the region and the proximity to the heart. Placement of a substantially cylindrical prosthesis in such a curved region can cause problems.
Stent grafts are typically deployed using endovascular techniques on an introduction device in which the stent graft is retained in a radially contracted condition by a sheath. Upon withdrawal of the sheath and release of any retention arrangement where provided, for example in cases in which the stent graft has self-expanding stents, the stent graft can expand under the action of the self-expanding stents towards the vessel walls to redefine the blood flow path. The introduction device is withdrawn after deployment.
Currently, stent grafts are deployed in curved lumens by causing these to follow the curvature imparted to the introducer. However, this can result in the stent graft not sitting properly in the blood vessel and in the lumen of the prosthesis being closed off or reduced in diameter. Kinks can also occur along the length of the prosthesis and these can cause problems with restriction of flow in the lumen.
Furthermore, when deploying a stent graft that is substantially cylindrical in a curved aorta there is a danger that the proximal end of the stent graft, that is, the end nearest the heart, will not lie flat against the walls of the aorta (i.e., is not positioned perpendicularly to the wall of the vessel) and blood can flow underneath the edge of the graft, particularly on the inner side of the curve of the thoracic arch and cause the stent graft to buckle and close off thereby causing serious problems.
U.S. Pat. Nos. 6,974,471, 2004/0073289, 7,318,835, 7,279,003 disclose prior art prostheses for implantation within a curved body lumen.
In general this application relates to the placement of prostheses in the aorta in the region known as the thoracic arch where the aorta leaves the heart and curves over in approximately a semi-circle to the descending aorta and then into the abdominal aorta and then into the lower limbs via the iliac arteries. The invention is, however, not so restricted and can relate to placement of prostheses within or in place of lumens in any portion of a human or animal body, though it is particularly relevant to curved lumens, particularly tightly curved lumens.